INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY #164

1. Headline: Reduction of Loss of Process Bath Liquor by

Mechanical and Other Means in a Semiconductor Plant

2. Background: See below.

3. Cleaner production Principle: Good housekeeping

4. Description of Cleaner Production Application:

Technology Principle: The technology uses spray rinsing,

in- process measures, and wastewater neutralization

and treatment to decrease heavy metals and lower

water consumption.

Case Study Summary

Process and Waste Information: The plant operates one

line in which copper products are stained and tin plated.

After the stain bath (with sulfuric acid and peroxide),

the work pieces are spray rinsed and the wastewater goes

to the water purification plant. After the plating in a

bath with lead and tin salts, the work pieces are spray

rinsed in two steps. The water of the first step goes to

the water treatment plant and the water of the second

spray is neutralized and sewered.

In line improvements include shortening the staining time

and adapting positions and holders. Process liquids are

removed from the work pieces by mechanical and physical

means. A wastewater treatment plant has been constructed

to treat plant water in a DND installation. Sludge is

concentrated in a filter press and retreated to remove

cadmium containing particles. The sludge is removed and

the water is sewered. The composition of the streams

leaving the plant are as follows:

Constituent Clean Stream Contaminated

Stream (mg/l)

(mg/l)

Lead 0.28 103

Tin <1 287 Copper 1.2 305 In the original operation, only one spray rinse after the tin bath was used. Wastewater was sewered without treatment and spent baths were taken to another plant of the same company. The in-line measures were undertaken in the early 1980's. Sludge is a new waste product. No new materials were introduced. The company claims that the measures have decreased heavy metals in the wastewater by 30%. However, it is difficult to compare the old and new situations since production has grossly increased. Scale of Operation: The capacity of the plant is 300,000 m2/yr. The plant operates 6000 hours/yr with 20 people working in the department. Stage of Development: All improvements are fully implemented. Level of Commercialization: All parts are widely available. Material/Energy Balances and Substitutions: The plant produces two water streams, a fairly clean stream which is sewered directly and a strongly contaminated stream which is combined with another dirty water stream from the factory before entering the DND installation. The balances for each are shown below. Clean Stream Dirty Stream Material Category Before After Before After Waste Generation (kg/yr): Lead 650 5.6 725 7.2 Tin 1350 <20 2010 <12 Copper 900 16.4 4.8 Sludge 0 150 Feedstock Use: N/A N/A Water Use: 45,000 20,000 7,000 from electroplating plant Energy Use: N/A N/A 5. Economics Investment Costs: Investment costs were Dfl 900,000. Capital costs were 180,000 Dfl/yr. Operational & Maintenance Costs: These costs for 1986 are as follows: Labor 90,000 Dfl/yr Chemicals 50,000 Sludge Removal 45,000 Energy 13,000 Payback Time: Annual savings were estimated at 378,000 Dfl/yr. Savings were not quantified so payback could not be calculated. 6. Advantages The improvements were made to reduce risks of accidents, reduce loss of copper and lower water consumption. According to company estimates the heavy metal content of the wastestream has been lowered by 30%. 7. Constraints: No information was provided. 8. Contact and Citation: Wastewater problems in the metal industry: results of interviews in 48 companies. Dr. Ir W. H. Rulkens, TNO, Maatschappelijke Technologie, postbus 342, 7300 AH Apeldoorn, Netherlands. TEL: 31-55-773344. Industry/Program Contact and Address: H.W. du Mortier VOM Jan van Eycklaan 2 Postbus 120 3720 AC Bilthoven Netherlands Phone: 31-30-287111 Fax: 31-30-287674 9. Keywords: the Netherlands, semiconductor, electroplating, good housekeeping, spray rinsing, heavy metal, stain, plating, sludge. 10. Reviewer's Comments: This case study was originally compiled by the UNEP IE Working Group on Metal Finishing. It underwent a UNEP IE funded technical review in 1994 for quality and completeness. It was edited for the ICPIC diskette in July 1995. ( DOCNO: DOCUMENT NOT AVAILABLE *****10-06)